1. Field of the Invention
The present invention generally relates to speech synthesis. More particularly, the present invention relates to a method and system for improving the intelligibility of synthesized speech at run-time based on real-time data.
2. Discussion
In many environments such as automotive cabins, aircraft cabins and cockpits, and home and office, systems have been developed to improve the intelligibility of audible sound presented to a listener. For example, recent efforts to improve the output of automotive audio systems have resulted in equalizers that can either manually or automatically adjust the spectral output of the audio system. While this has traditionally been done in response to the manipulation of various controls by the listener, more recent efforts have involved audio sampling of the listener's environment. The audio system equalization approach typically requires a significant amount of knowledge regarding the expected environment in which the system will be employed. Thus, this type of adaptation is limited to the audio system output and is, in the case of a car, typically fixed to a particular make and model of the car.
In fact, the phonetic spelling alphabet (i.e., alpha, bravo, Charlie, . . . ) has been used for many years in air-traffic and military-style communications to disambiguate spelled letters under severe conditions. This approach is therefore also based on the underlying theory that certain sounds are inherently more intelligible than others in the presence of channel and/or background noise.
Another example of intelligibility improvement involves signal processing within cellular phones in order to reduce audible distortion caused by transmission errors in uplink/downlink channels or in the basestation network. It is important to note that this approach is concerned with channel (or convolutional) noise and fails to take into account the background (or additive) noise present in the listener's environment. Yet another example is the conventional echo cancellation system commonly used in teleconferencing.
It is also important to note that all of the above techniques fail to provide a mechanism for modifying synthesized speech at run-time. This is critical since speech synthesis is rapidly growing in popularity due to recent strides made in improving the output of speech synthesizers. Notwithstanding these recent achievements, a number of difficulties remain with regard to speech synthesis. In fact, one particular difficulty is that all conventional speech synthesizers require prior knowledge of the anticipated environment in order to set the various control parameter values at the time of design. It is easy to understand that such an approach is extremely inflexible and limits a given speech synthesizer to a relatively narrow set of environments in which the synthesizer can be used optimally. It is therefore desirable to provide a method and system for modifying synthesized speech based on real-time data such that the intelligibility of the speech increases.
The above and other objectives are provided by a method for modifying synthesized speech in accordance with the present invention. The method includes the step of generating synthesized speech based on textual input and a plurality of run-time control parameter values. Real-time data is generated based on an input signal, where the input signal characterizes an intelligibility of the speech with regard to a listener. The method further provides for modifying one or more of the run-time control parameter values based on the real-time data such that the intelligibility of the speech increases. Modifying the parameter values at run-time as opposed to during the design stages provides a level of adaptation unachievable through conventional approaches.
Further in accordance with the present invention, a method for modifying one or more speech synthesizer run-time control parameters is provided. The method includes the steps of receiving real-time data, and identifying relevant characteristics of synthesized speech based on the real-time data. The relevant characteristics have corresponding run-time control parameters. The method further provides for applying adjustment values to parameter values of the control parameters such that the relevant characteristics of the speech change in a desired fashion.
In another aspect of the invention, a speech synthesizer adaptation system includes a text-to-speech (TTS) synthesizer, an audio input system, and an adaptation controller. The synthesizer generates speech based on textual input and a plurality of run-time control parameter values. The audio input system generates real-time data based on various types of background noise contained in an environment in which the speech is reproduced. The adaptation controller is operatively coupled to the synthesizer and the audio input system. The adaptation controller modifies one or more of the run-time control parameter values based on the real-time data such that interference between the background noise and the speech is reduced.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.